According to Collectors Weekly, porcelain signs were made of rolled iron or steel, die-cut to shape, with layers of powdered glass fused to the sign's surface. This type of weather-resistant signage was manufactured between the late 19th century and the mid-20th century for outdoor advertising.
Antique porcelain signs form a significant category of advertising collectibles. Due to their increased popularity, the market has also been flooded with reproductions of classic vintage porcelain sign designs. One way to tell whether a porcelain sign is a modern fake is to examine the layers of porcelain. On many originals, the first layer was white enamel, with other colors layered on top; modern counterfeits tend to have a flush, even layer of paint.